Method of making esters from nitriles



Jan. 27, 1931. L. J. CHRISTMANN 0,

METHOD OF MAKING ESTERS FROM NITRILES I Filed March 30, 1926 8 9 /6 /7 4 HCN 63L1 Alcqhol Toluol Hc|som 93mm ,v v

NuOH

Lacfoniirile v Waier 2 2 3;; I 1

Main Reucrion n FiH'er Vacuum I gm 4 Residue I Arrpos. Sh" 1e Firs? Fralcfion Y EH15] w NH CI Laofaie 657H 5O INVENIOR v Ludwig J. Chrlsfmann ATTORNEY operations, I add tothe succeeding operation Patented Jan. 27, 1931 ,Various methods for the manufacture of jijaazez LUnwIe J. cHRIsTMANn, or NEW YORK, 1v. Y., ASSIGNOR To Aivieiaichn orAnAM n' COMPANY, OFNEW YORK, 1v. Y., A CORPORATION OF MAINE METHOD OF MAKIN ESTERS'EROM NITRILES i App1ica.tion filed March 30, 1926. Serial No. 98,408.

This invention relates to the production of esters from nitriles, more particularly to the esters of hydroXy-acids, such as lactic acid.

esters or lactic acid, for instance, ethyl lac- 1 tate have been proposed. Oneof such methods consistsin providingfa mixture of lacto: nitrile,ethylalcohol and water, and causing the same to react in the presence of sulphuric acid in accordance' with the following 7 equationrw V 2C:H5OH+2OH CHOHCN+2HzO+H2SO4= 1' In this process a large excess of alcohol was ester shall be high.

used,generally about 5-mols per mol of lactonitrile, whereas theoretically the two combine'in equal proportions, andthe yield of ethyl lactate was-rather low, about 30%-.to

The present invention is an improvement over the aforesaid method, it being among the objects thereof to provide a method 01": making' esters from nitriles" which shall not require-the use of a large excessiof alcohol and in .whichthe etlic'ienoy of conversion to the I Ihave foundas the result of a long'investi- I gation that the efliciency ot the above reacs used and addingto the-reaction mixture as a tion, for instance, may be increased considerably and the cost ofproduction decreased by greatly reducingthe amount of the alcohol diluent or solvent, a hydrocarbon which does not enter'into the react1on., fIn aser es of the residue frointhe precedingoneand thus further increase the eff ciency thereof. I also prefer tousehydrochloric acid as the hydro- ,lyzingomediuin in the process.

as" large' an excess of alcohol, asiheretofore.

To this mixture is added an organic diluent in which the ingredients are soluble, but

which does not'enter into'the reaction,-such as toluolfl 'I-Iydrochloric acid gas ispassed I :into themixture until the amount calculated to cause a complete reaction has beenabsorbed, after which the reactionvessel is heated for several-hours.

Ammonium chloride, which is formed inthe reaction is filtered oiiand the filtrate-is distilled under re duced pressure, the condensate containing the ethyllactate, which is then sep arated from the'toluol and the excess of alcohol;- The yield of ethyl lactate by this'process is high, from 'to48 5% or" the theoretical andthe projductis substantially pure. The'operation' is repeated addingthe distillation residue to the reaction mixture whereby theefiiciency 0t the-second operation'is' increased to to "A specificexample of the invention is as follows operation ofthe -;A' reaction vessel isprovided with a; stirring'device and a reflux'condenser, and in'the gsame 'is'placed parts of 95% la'otonitrile togcther with'l50 parts of 93% ethyl alcohol, lOpartsofwater and l00tpartsof toluol, all

quantities being by-weight. Into this mixture is passed 80 parts by weight of hydrochloric acidgas, the amount of. gas passed 7 inbeing determlnedby any suitablemeans.

such as afiojw-meter, or by noting the increase in weight ofthe 'rea'ctionyessel, after which the mixture is heated with the reflux and with stirring for aboutl' l hours, forming ethyl lactate bythe "followlngrea'ction; O2H5OH+CHaCH0HCN+H2O+HC1=' ".onaononooooznwNmci' Thewaternecessary forthe reaction is de- 5 rived principally from the water intheethyl alcohol and the lactonitrile, but part of the were produced in aside reactionwhich results in the formation of ether and water from someoithe alcohol present. After the completionofthe reaction the ammonium chloride: formedis filtered oli and washed with toluol. The combined filtrate is diso tilled in" a vacuum and the condensate coming" over 'up-to 85 C. at37 mm. pressure is colle'ct ed. i It contains the; ethyl lactate, toluol and alcohol, which maybe separated by fracj e tionaldistillation .'orby. other well knownv means, or thefractionalseparation-maybe made during the initial. distillation; Theefliciency of thereactionis about%.i-

Theresidueof the vacuumdistillationfcom I sists principally of lactide and represents a loss, as ordinarily it cannot be converted into lactate during the course of the reaction. However, I have made the unexpected and remarkable discovery that when this residue is added to the reaction mixture it increases the efficiency of conversion to agreat degree. For example, I may take the residue resulting from the operation of the above example, and add the same to a similar reaction mix ture of 150 parts of 95% lactonitrile, 150 parts of 93% ethylalcohol, 10 parts of water and 100 parts of toluol, pass in 80 parts ofhydro} chloric acid gas and conduct-theoperation as before. In this case the efiiciency of the conversion-into lactate is about9i%.

This phase'o'f my invention may be used successfully to increase the yield of'lactate even when no diluent,-suchas toluol,is used. l'may cause a reaction'to take place between 150-parts of 9570' lactonitrilc, 2. 5 parts of 93% ethyl alcohol and 78 parts of hydrochloric acid gas and obtain a yield of about 69% of ethyl lactate; Iia similar run is made with the addition of the distillation residue produced in the previous operation,

the yield isincreasedfand it a series of runs is'made, -adding to each run the residue from the preceding, the etliciencyof the reaction maybe gradually incre'asedto about 85%. WVhen a diluent, such as tol'uol, is used, the initial eflicien'cy is higher, the maximum efliciency is higher and the maximum efficiency is reached with fewer operations.

' A modification-0t the process consists in the use in the reaction mixture of a chloride from which the necessary hydrochloricacid may be generated. In accordance therewith I may, place 150 parts of 95%lactonitrile in the reaction vessel and add thereto 150 parts or" 98% ethyl alcohol, 250 parts of toluol and 155 parts of calcium chloride. Into this mixtureis dropped l lOparts'cf 96% sulphuric acid at such a rate that the mixture does not heat up to boiling, the mixture being vigon ously stirred during the additionjof the acid. he stirring is continued for about two hours. and the reaction mixture is The accompanying drawing is a -diagram matic view or flow sheetof one mode of operation of my invention.

Lactonitri le 1 is made by slowly adding liquid hydrocyanic acid 2 toacetaldehyde 3 in the cold and in the presence of a small,

amount of caustic soda 4'. Hydrochloric acid gas 5 is generated from a solution of hydrochloric acid 6 and concentrated sulphuric acid 7 by dropping the former onto the latter.

Lactonitrile 1, alcohol 8, toluol 9 and water 10 are placed in the main reactlon vessel -11,

hydrochloric acid gas 5 is led into the same, and the mixture is heatedwith a reflux for several hours. The product "is filtered at 12 and the precipitate ot'an'imonium chloride 13 is removed. 7 The filtrate is distilled in vacuum still 14 and the residue 15 is returned to the vessel 11,. the distillate being redistilled in atmospheric still 16, the first fraction 17 is returned to vessel 11,'and the remainder of the distillate is ethyl lactate 18 of commerce. The residue 19 from the hydrochloric acid gas generator 5' is a sulphuric acid.

My method is equally well adapted for the preparation of other lactates, for example,

methyl lactate. This I have accomplished in the same manner asabove with the substitu tion of methyl alcohol for the ethyl alcohol; using gaseous hydrochloric acid, and also by generatinglthe same in the-mixture. Noris my invention limited to. the production of methyl and ethyl lact'ates as I have success iully operated my process with other alcohols than methyl-and ethyl. It is not essential that lactonitrile or even other hydroxy-nitriles be used, as many othernitriles are adaptable to my process, resultingin the productionoi a series of esters of the corresponding acid, In. my description of the operation of the invention-I have set-forth the useof toluol as a diluent but many other substances, such as benzohxylol and other hydrocarbons,especially cyclic hydrocarbons, are Well adaptedto my process. The details of the proportions of the ingredients, and the conditions of the reaction and. ot the subsequent distillation may be changed insubstantial respects withl out departing from the principles herein set forth. These and other changes maybe made in my invention, the scopeof which is defined in-the claims appended hereto.

-What I claim-is: a

1. A method of making; esters which comprises providing a mixture of a nitrile and an alcohol in approximately theoretical combining proportions, andtrea-ting from nitriles the mixturewith an inorganic acid generated in'situ to give substantially complete reaction.

2. A method of making esters from nitriles which comprises providing a mixture of a nitrile and an alcohol in approximately theoretical combining proportions, adding an inert diluent thereto, and treating the mix ture with an inorganic acid.'i i

8. A method of making esters from nitriles which comprises providing a mixture of a nitrile and an alcohol in approximately theo retical combining proportions,- adding toluol thereto, and treating the mixture with an inorganic acid.

l. A method of making esters from nitriles which comprises providing a mixture of a nitrile and an alcohol inapproximately theoreticalcombining proportions, adding an inert diluent thereto, and treating the mixture wlth annorganic acid in a gaseous state.

5. A method of making esters of lactic acid which comprises providing a mixture of lactonitrile and an alcohol in approximately theoretical combining proportions, adding an inert diluent thereto and treating the mixture with hydrochloric acid.

"with an inorganic acid, filtering off the insoluble matter, distilling off the ester, and returning the distillation residue to the reac-' tion.

7 tonitrile and an alcohol inapproximatelythe oretical combining proportions, adding an inert diluent thereto, treating the mixture with hydrochloric acid in the presence of a limited amount of water, heating. the reaction mixture, filtering 0E the precipltate formed, and distilling the filtrate in a vactonitrile and alcohol in approximately theoretical combining proportions,adding an inert cyclic hydrocarbon solvent thereto, treating the mixture with gaseous hydrochloric acid in the presence of alimited amount of water, heating the reaction mixture, filtering off the precipitate formed, distilling the filtrate-in a Vacuum, and returning the distillation residue to the reaction;

9. A method of making esters from nitriles which comprises providing a mixture of a nitrile and an alcohol in'approximately theoretlcal combining proportions, and treatlng the mixture with hydrochloric acid generated in situ by the action of sulphuric acid upon calcium chloride, to give substantially complete reaction. Y

In testimony whereof, I have hereunto subscribed my name this'Qtth dayof March 1926.

LUDWIG J CHRISTMAN N.

7. A method of making esters of lactic acid. which comprises providing, a mixture of lac- 8. A method of making esters of lactic acid which comprises-providing a mixture oflac- V 

